At the end of the 2018 season, the Boston Red Sox were celebrating their fourth World Series title since 2004. But according to our experts, even with almost all of the Red Sox's star players due back this year, taking another title won't be easy. They barely won out the top spot in our preseason poll, edging out the Houston Astros (the 2017 champs) and their archrivals, the New York Yankees. Those three teams split all of the first-place votes with the Red Sox and Astros getting six apiece and the Yankees getting the remaining three.

Opening Day on ESPN and ESPN+

A new MLB season is upon us, and what better way to celebrate than with a schedule packed with Opening Day matchups?

The Los Angeles Dodgers are favored to be the top team in the National League for a third straight year, but is this the season they finally break through and beat the American League champs to win their first World Series since 1988? The Dodgers were the only NL team to get third-place votes outside of the AL's top trio (they got two). However, the NL's stronger competitive balance shines through, with eight of the top 12 teams coming from the Senior Circuit, including three teams apiece from the NL East and NL Central.

That balance doesn't end there. The teams ranked Nos. 11-16 all got votes placing them in the top 10, so which teams are on top are sure to get shaken up as the season gets underway.

For every team, we identified the best- and worst-case scenarios and the one player who could make or break the season. We also included the projected records and division finishes calculated by Bradford Doolittle, as well as the most recent World Series odds calculated by the Westgate Las Vegas SuperBook.

Best case: It will be nearly impossible to match last season's 108 victories -- the most in Red Sox history -- but with almost everyone back from 2018, including MVP Mookie Betts and RBI champ J.D. Martinez, the talent is here to become the first repeat World Series champion since the 2000 Yankees.

Worst case: Is there a scenario in which the Red Sox don't even make the playoffs? Sure. The Yankees win the division and the Rays win, say, 95. In the AL Central, the Indians and Twins beat up on a terrible division and both win 90-plus games. Meanwhile, one of Boston's big stars goes down, the bullpen struggles and the Red Sox win 90 and still miss the postseason.

Make-or-break player: Yes, the bullpen is a concern, but if the Red Sox are going to beat out the Yankees, they'll need a healthy and dominant season from Chris Sale. He ended last season with a sore shoulder after spending time on the injured list and throwing 56 fewer innings than he did in 2017. They didn't need those innings last year, but with less depth in the bullpen, those innings will matter in 2019. -- David Schoenfield

Best case: Shortstop Carlos Correa stays healthy for a change, second baseman Jose Altuve shows no ill effects from his offseason knee surgery and ace Justin Verlander continues to flip the bird at Father Time. If all that happens, Houston could become the first team since the 2002-04 Yankees to win 100 games in three straight seasons.

Make-or-break player: In the 25 games that Altuve missed last season, the Astros won at a .440 clip (11-14). In the games he played, they posted a .671 winning percentage (92-45). So yeah, the former MVP kinda matters. But don't underestimate the importance of McHugh. After a year of exile in the pen, the Astros are counting on him to fill Keuchel's sizable shoes. That's no easy feat, especially for a guy who has averaged just north of 70 innings over the past two seasons. -- Eddie Matz

Best case: At the start of spring, Brett Gardner bluntly gave his assessment of where the Yankees should end 2019. For his squad, the outfielder believes it's all about the World Series. "Anything short of that is not acceptable," he said. For a group that was a game away from the World Series two years ago and lost in the American League Division Series to the eventual champs a year ago, the Yankees have flirted with the championship round long enough.

Worst case: Given the history of success in the Bronx, making the postseason is always goal No. 1. With a division that's getting stronger, that objective won't be easy to attain. So, the worst-case scenario -- which still seems a far-fetched concept at this point -- would be if the injury bug that's set in this spring persists deep into the season, causing the Yankees to fail to get past the Red Sox or qualify for a wild-card berth.

Make-or-break player: Perhaps no spring training injury has been as concerning for the Yankees as Luis Severino's. The right-handed starter's shoulder inflammation appears to be something the club can manage for now, but what if it becomes a deeper issue later in the season? Though New York certainly addressed weaknesses in its rotation this offseason, it didn't expect its ace to start the season on the injured list. -- Coley Harvey

Best case: The Dodgers will once again benefit from baseball's best starting pitching depth. Their biggest concerns last season revolved around the back end of their bullpen and their success -- or lack thereof -- against lefties. But hard-throwing reliever Joe Kelly was signed to shore up the former, and right-handed-hitting center fielder A.J. Pollock should help the latter. The Dodgers have an embarrassment of riches, both on their 40-man roster and in their farm system. They also reside in a bad division.

Worst case: Their ace, Clayton Kershaw, and their closer, Kenley Jansen, are both seemingly trending in the wrong direction, each of them coming off disappointing 2018 seasons -- by their standards -- and costing more than $41 million combined in 2019. Their continued struggles could cause a lot of disruption. The Dodgers are also banking on Max Muncy duplicating his stunning success from last summer and Corey Seager returning to the All-Star form he displayed in 2017. Neither is a guarantee.

Make-or-break player: Kershaw, who signed a three-year, $93 million extension only days after a second consecutive defeat in the World Series. He is a first-ballot Hall of Famer already, but he also compiled nearly 2,250 innings before his age-31 season, missed time each of the past three years with a back injury and suffered a drastic velocity drop last season. The Dodgers have young starting pitching to build around with Walker Buehler and Julio Urias, but they probably need a close-to-elite Kershaw in 2019. -- Alden Gonzalez

Best case: Manager Craig Counsell can play both the "unfinished business" card as well as the "disrespected" card even though the Brewers got all the way to Game 7 of the NLCS last year. Las Vegas has their over/under at just 86.5 wins and there's little doubt many will pick the Cubs or Cardinals to unseat them at the top of the division. On the field, they are as deep as ever, and there's no reason reigning MVP Christian Yelich can't pick up where he left off. He's in his prime -- and so are the Brewers.

Worst case: It's possible all those questions about their starting pitching prove to be warranted, as Milwaukee's strategy of creatively getting 27 outs eventually backfires. Most of that revolves around Josh Hader, who gives Counsell the ability to cross off six to nine outs almost every time he pitches. Milwaukee did little to upgrade on the mound, probably because it all worked last season. The Brewers also played the best possible baseball and barely squeaked by in the division. One ounce of complacency could cost them.

Make-or-break player: There's probably a few starting pitchers you could choose from, but it really has to come down to Hader. He's such a luxury for a manager, and if he's limited or ineffective in any way, the Brewers will have to change their plans on the fly. Their offense is deep, and the rest of the staff has its roles, but Hader gives them so much on the days he pitches. He remains the key. -- Jesse Rogers

Best case: The Cubs stay healthy and reach peak potential out of a starting staff made up of five No. 2 and 3 pitchers, while their offense returns to a walking/slugging mentality that they abandoned last season. It wouldn't hurt if closer Brandon Morrow returned in May and gave them a solid -- and healthy -- five months. But most of the Cubs' success will involve that aging rotation and the middle of the order. On paper, the names scream talent and potential.

Worst case: It's possible the rest of the NL truly has caught up to the Cubs, as the Brewers proved last year, while the ceilings both on offense and on the mound are much lower than the team anticipates. As is, they don't have a true No. 1 -- think Scherzer, deGrom or Nola -- and their offensive production in the outfield looks about the same as a year ago. In other words, not very good. And if Morrow can't deliver, it puts a huge strain on the rest of the pen -- as well as the front office. They'll likely need to get ninth-inning help.

Make-or-break player: Catcher Willson Contreras is a key on several fronts. First off, he's catching a low-velocity, high-pitchability staff. Cubs starters simply aren't going to be blowing anyone away, which means he'll have to steal as many strikes as he can -- an area of the game he's been working on. He's also very important on offense simply because he needs to make up for a lack of production in the outfield. -- Rogers

Best case: If the Indians' rotation lives up to its billing, and if the Cleveland front office is motivated by a little pressure from the other clubs in the AL Central, Cleveland has plenty of time to identify and fill the remaining holes on its roster before the postseason. Once the Indians are back in October, hot streaks from that star-studded rotation and elite hitters Jose Ramirez and Francisco Lindor can steer Cleveland past the rugged AL playoff field and to its first title in 71 years.

Worst case: An injury to one of the stud starters and a mushrooming of the potential signs of a Corey Kluber decline could put Cleveland in an early hole, opening the door for the Twins. Even that might not be enough, and given the Indians' talent edge, an off season from Ramirez or Lindor may have to play a part as well. In any event, if the Indians are facing a sizable deficit in the division when we hit July, we might see the front office decide to reset.

Make-or-break player: The Indians gambled by trading away veteran catcher Yan Gomes, which puts Roberto Perez squarely under the gun. Perez has been one of baseball's better defensive catchers in a part-time role for a few years. But can he continue that work with the vaunted Cleveland staff in a larger role? Forget his bat -- if there is any drop-off in Cleveland's pitching stemming from the loss of Gomes, that's a major problem. -- Bradford Doolittle

Best case: If Josh Donaldson has a healthy comeback season and Ronald Acuna Jr. improves upon his epic rookie season, the Braves have the potential to light up SunTrust Park like a pinball machine. Spring injuries to the pitching staff are a concern, but there are enough high-level arms in Atlanta's organization to make it work. There is a reason the Braves weren't that aggressive during the offseason: This is a stacked system.

Worst case: Alas, you can't assume that Acuna's arc will continue skyward. He's going to be great, but these developments don't always unfold in an orderly fashion. If the league adjusts to him, Donaldson gets hurt again and younger Braves like Dansby Swanson and Ozzie Albies don't take a step forward, scoring all of a sudden becomes a problem. If that happens, then the club will come under scrutiny for not pursuing Bryce Harper or Manny Machado.

Make-or-break player: One thought on the Braves' approach to the winter is that they didn't need a decade of Harper or Machado. They needed one season of that, as Acuna and Albies are still on the climb and will soon be joined by the likes of Austin Riley and Christian Pache. That one, star-level season will hopefully be provided by Donaldson, an MVP candidate when healthy. The problem: Donaldson has not been able to stay healthy. -- Doolittle

Best case: Starters Max Scherzer, Stephen Strasburg and Patrick Corbin finish 1-2-3 in the Cy Young voting. Juan Soto builds on his standout rookie campaign and, at the age of 20, breaks Bryce Harper's record for the youngest unanimous MVP in baseball history. Adam Eaton stays whole, Trea Turner steals 100 bases and Victor Robles wins Rookie of the Year, as the Nationals -- who have never won so much as a single playoff series -- win the World Series in year one A.B. (After Bryce).

Worst case: Scherzer proves that, contrary to popular belief, he's human. Strasburg proves that bionic elbows do, in fact, have a time stamp. And Corbin proves that his 2018 was a mirage. A thin bullpen can't mask the rotation's woes, and the offense sputters in Year 1 A.B. The Nats miss the playoffs for a second straight season. Even worse, they're forced to watch as Harper wins his second MVP and leads the Phillies to a championship.

Make-or-break player: Since coming to D.C. in 2017, Eaton's .394 on-base percentage is 11th best in the NL (min. 100 G). The problem is, his on-field percentage is only .364 (as in, he has missed 64 percent of Washington's games). For the Nationals to do what they believe they can do, they'll need Eaton to be a regular fixture in the lineup -- not just at the top of the order, but also in right field, where he should be a significant defensive upgrade over the guy who used to play there. -- Matz

Best case: It's all on the table for a team that hasn't posted a winning record since 2011. The offense should be one of the league's best, especially if a certain high-profile free-agent acquisition pays off. The defense? Well, it can't be worse, right? The bullpen looks strong, whether or not the Phils add to the back end. That puts the onus on a top-heavy starting rotation. Aaron Nola must approximate his great 2018 season; Jake Arrieta needs to remain a legit No. 2; and Nick Pivetta, Zach Eflin and Vince Velasquez need to nail down their spots. If the Phillies get strong starting pitching from stem to stern, they will win the NL East.

Bryce Harper's Phillies debut on ESPN+

After signing a $330 million deal over the winter, Philadelphia's new superstar takes the field in front of his new home crowd for the first time. Don't miss Harper's debut!Watch Braves-Phillies, 3 ET on ESPN+

Worst case: What if, in Year 1 of 13, Bryce Harper hits .230? The Phils could find that their window of contention, which seems to just be opening, is stuck. Those Phillies fans standing outside looking through it? You don't want to hear what they are saying.

Make-or-break player: Clearly, this season will be all Harper, all the time in Philadelphia. His defenders see his 2015 season as more representative of his true talent level than what has occurred since then. Vegas sees him as the odds-on favorite to win this season's NL MVP. His detractors say we've already seen the best of Harper and that he's too inconsistent to be considered an upper-level star. For better or worse, Harper and the city of Philadelphia are in it together. -- Doolittle

Best case: The Cardinals will be in the thick of it if Marcell Ozuna can bounce back from a down season to form a dynamic offensive threesome with Matt Carpenter and perennial MVP chaser Paul Goldschmidt. If the Cardinals' rotation stays healthy and manager Mike Shildt is able to piece together a plus bullpen, which may include longtime prospect Alex Reyes and definitely will include Jordan Hicks and Andrew Miller, St. Louis might well emerge as the division's best team.

Worst case: There is a lot of upside to the St. Louis staff, but there is also a populous mix of injury question marks and youngsters. If the injuries come in waves and the kids aren't ready to pick up the slack, that would be enough to push the Cardinals down in the standings of the very deep National League.

Make-or-break player: When Harrison Bader took over in center field last season for the Cardinals, it changed the complexion of what had been a suspect defense. He'll be back in center again, giving St. Louis exceptional defense up the middle. But Bader needs to continue to progress with the bat so Shildt can keep his glove in the lineup. -- Doolittle

Best case: It took a 163rd game for the Dodgers to win the NL West in 2018, so the Rockies hope to go one game better this season and capture the first division title in franchise history. From there, the goal is even bigger: Win the first World Series in franchise history. They have an MVP candidate in Nolan Arenado. And Trevor Story put up almost identical numbers in 2018, so that's two MVP candidates. The rotation was very good in 2018. The biggest issues: the bullpen (which lost Adam Ottavino) and Ian Desmond's ability to play center field on a regular basis.

Worst case: The projection systems see the Rockies as a .500 team, but that feels more like a worst-case scenario than a median outcome. Still, if Kyle Freeland and German Marquez regress (or get injured, always an issue with Rockies starters), the rotation could fall apart. Desmond could be a disaster in the field and at the plate. The bullpen leaks. They finish under .500, and Arenado questions why he didn't wait for free agency.

Make-or-break player:Jon Gray. He could be great (3.67 ERA in 2017) or not great (5.12 ERA in 2018). The big strikeout rate was still there last year, so there's no denying the stuff remains elite. -- Schoenfield

Best case: After winning 90 games last year, including an impressive 41-25 mark in the second half, the Rays clearly have their sights on returning to the playoffs for the first time since 2013. Beating out the Red Sox and Yankees won't be easy, but 95 wins and a wild card fits into a best-case scenario. Of course, the best best-case would be the Red Sox and Yankees suffer some injuries, Blake Snell wins another Cy Young Award, Willy Adames makes The Leap, young hitters like Austin Meadows and Brandon Lowe break out, the bullpen is dominant again and they win 99 games and shock the world with a division title.

Worst case: The team allowed just 646 runs last year, second-fewest in the AL. There is a lot of projected regression here, not just from Snell -- good luck repeating that .088 average allowed with runners in scoring position -- but from some of the relievers. The Rays were next to last in home runs, and their top returning home run hitter is Adames, with 10. Combine pitching regression and questionable power output, and they fall back to .500.

Make-or-break player:Tommy Pham. He was 11th in NL MVP voting with the Cardinals in 2017 and tore it up in 39 games with the Rays. If he can post a .280/.400/.525 line, the Rays will have the elite offensive player they need. -- Schoenfield

Best case: Despite all of the changes the Mets have made since the beginning of last season, the story for New York is much the same. Simply put, the Mets need their core players to remain mostly healthy for the full season and, in particular, they need to get 140 or more starts from their primary starting pitchers. If that happens, there is enough high-level talent spread across the roster to put the Mets in the middle of a four-way battle for the NL East.

Worst case: More than any other team, the Mets' worst case is the flip side of its best case. As the season opens, the Mets are looking at a half-season without Yoenis Cespedes, and will likely open the season without Jed Lowrie or Todd Frazier. New York's big-league depth is improved, but there isn't much likely help in the minors, beyond the possible exception of slugging first baseman Pete Alonso. In a rugged division, the Mets can't afford another injury epidemic.

Make-or-break player: For the Mets to win the East, they need Noah Syndergaard to rejoin Jacob deGrom in the Cy Young chase. For Thor, the strikeout total is the tell. If he's around 200, then that means he's missing starts. If he's up around 270-280, he's having the kind of career season that might put the Mets over the top. -- Doolittle

Best case: Winning 97 games again would be a great scenario. In a perfect world, something goes wrong in Houston and those 97 wins are enough to capture the AL West title. And once you get into the postseason, anything can happen. It seems like everything goes wrong in the playoffs for the A's in the Billy Beane era -- 0-for-9 in reaching the World Series -- but maybe this is the year everything goes right in the playoffs.

Worst case: The starting pitching was held together last year by duct tape and Elmer's glue as the A's churned through 15 different starters (including trying the "opener" strategy down the stretch). Their top two guys from last year are now injured (Sean Manaea) and with the Angels (Trevor Cahill). This year, they're counting on Marco Estrada, Brett Anderson and rookie Jesus Luzardo to make an impact. The rotation could be a disaster and the A's struggle to finish .500.

Make-or-break player: Probably one of the starters, but closer Blake Treinen broke out from career mediocrity to go 9-2 with 38 saves and a 0.78 ERA. He led all pitchers in win probability added, meaning he was great in close games and clutch situations. -- Schoenfield

Best case: Like last year, the Angels enter 2019 with the chance to earn a wild-card berth if they stay relatively healthy. Mike Trout raises their floor tremendously, while Justin Upton, Kole Calhoun and the criminally underrated Andrelton Simmons help make up what looks like an above-average lineup. If the Angels can get, say, a combined 100 starts from the foursome of Andrew Heaney, Tyler Skaggs, Matt Harvey and Trevor Cahill, and if the high-powered arms in their bullpen perform, they'll make a push.

Worst case: So, about those injuries -- the Angels were forced to use 60 different players in 2018, and this is not an organization with enough depth to sustain something like that. The veterans they brought in on one-year contracts -- Harvey, Cahill, closer Cody Allen, catcher Jonathan Lucroy and first baseman Justin Bour -- are all major questions this season. If they don't turn their careers around, it'll be a fifth consecutive postseason absence. In other words, another wasted season of Trout.

Make-or-break player:Shohei Ohtani is important for this coming season, but he means everything to the Angels' future. Ohtani will spend this season as a DH who is also rehabbing from Tommy John surgery, hopeful of resuming a two-way role in 2020. He could be the most valuable player in the sport by then, but his rehab needs to go smoothly. And there is no blueprint for it. -- Gonzalez

Best case: The Twins have bounced around from 70 wins to 83 to 59 to 85 (and a wild card) to 78 the past five seasons. They signed Nelson Cruz and C.J. Cron, who combined for 67 home runs last year (Twins DHs and first basemen hit 32 in 2018). They'll need the 2017 version of Byron Buxton and somebody in the rotation -- Michael Pineda? -- to step up behind Jose Berrios and Kyle Gibson. If all that comes together and the Indians' rotation falters a bit, the AL Central crown is possible.

Worst case: The same issues pop up that plagued them in 2018. Buxton and Miguel Sano don't hit. Cron turns into Logan Morrison. Cruz gets old overnight. The back of the rotation stinks, and the bullpen struggles. Even in a weak division, they finish under .500.

Make-or-break player: Buxton. He was worth 5.2 WAR in 2017, when he hit .253/.314/.413 and caught everything between North Dakota and Wisconsin. He batted just 94 times in 2018, hit .156 and was worth minus-0.2 WAR. -- Schoenfield

Best case: The newcomers to the rotation -- Sonny Gray, Alex Wood, Tanner Roark -- all pitch well, giving the Reds their best rotation in years. Joey Votto rediscovers his power stroke. Yasiel Puig has his best season. Rookie Nick Senzel makes an immediate impact in center field. Both FanGraphs and PECOTA projections see the Reds as a .500 team in a tight five-team race. If the breaks go their way, a division title is possible (FanGraphs gives a 7.5 percent chance of that happening).

Worst case: The rotation is still terrible, Votto hits 12 home runs again, Puig becomes a distraction and Scott Schebler ends up playing 140 games in center. The Reds lose 90 again in a tough division.

Make-or-break player: Gray. The Reds were 27th in rotation WAR in 2018, 29th in 2017 and 30th in 2016. Yuck. One guy won't turn that around, but given the lengthy extension Gray signed, the Reds are hoping he can be a top-of-the-rotation starter. -- Schoenfield

Best case: There is a non-zero chance that the Pirates' pitching staff emerges as the best in the NL. The rotation has dynamism in Jameson Taillon and, hopefully soon, Mitch Keller, along with good depth. The back of the bullpen with Felipe Vazquez, Keone Kela and Richard Rodriguez looks outstanding, especially if Clint Hurdle can identify a dependable group of bridge guys. If that staff is supported by plus defense and a lineup that gets a couple of career seasons, then Pittsburgh is capable of fringe contention.

Worst case: The pitching is OK, but the worry is that the offense looks as feeble as it might, especially given a less-than-scary middle of the lineup. Meanwhile, if the Bucs manage to hang near the fringe of wild-card contention heading into July, the need for a thumper would become obvious to all. But if the trade deadline passes without the addition of said thumper, sooner or later the Pirates need to throw their fans a bone or three.

Make-or-break player:Chris Archer looks like the No. 3 or 4 in the Pirates' prospective rotation, but if he returns to form, that's when the Pittsburgh staff begins to approach its potential. Hopefully pitching coach Ray Searage can work his magic, as he has done so often before. -- Doolittle

Best case: They've lost Patrick Corbin, but Zack Greinke, Robbie Ray, Zack Godley, Luke Weaver and Merrill Kelly have the potential to emerge as an above-average rotation. Jake Lamb and Steven Souza Jr. combine for the 60 home runs they hit in 2017 rather than the 11 they hit in 2018. Adam Jones finds the fountain of youth. Somebody locks down the ninth inning, a big problem last year. Look, the Dodgers have won six straight division titles. They have depth and star power that Arizona lacks. A lot will have to go wrong in L.A. for Arizona to have a chance to win the division, so maybe a wild card is the best-case scenario.

Worst case: They can't replace Paul Goldschmidt, Corbin and A.J. Pollock, who combined for 12.7 WAR in 2018. The offense was ninth in the NL in runs last year and craters without Goldschmidt. The bullpen isn't fixed. If the Padres and Giants are better, it could turn into a 90-loss season.

Make-or-break player: Ray has as good stuff as any lefty in the game, and it all came together in 2017, when he went 15-5 with a 2.89 ERA. He maintained his sky-high strikeout rate in 2018, but he walked too many batters and had some minor injury issues. If he returns to All-Star level, he and Greinke give Arizona one of the best 1-2 tandems in the majors. -- Schoenfield

Best case: The Mariners haven't made the playoffs since 2001, the longest drought in the majors. They've won 89, 86 and 87 games in three of the past five seasons -- totals that could have made the postseason in 2015 or 2017, except those seasons they finished under .500. Can they finally get their timing right? Hey, if they get bounce-back seasons from Jay Bruce and Domingo Santana (66 home runs in 2017, 14 in 2018), and Yusei Kikuchi is the real deal, and Marco Gonzales takes another step forward, and the no-name bullpen delivers, and Justus Sheffield comes up and lights it up ... OK, that's a lot of ifs. This isn't a complete teardown, but a .500 season would be a good season.

Worst case: There's a lot of downside here, with the age of the lineup and the lack of depth on the pitching staff. The Mariners lost five of their top six players from 2018. Things could easily spin out of control, which could lead to Mitch Haniger getting traded and something approaching 100 losses.

Make-or-break player:Hunter Strickland. The Mariners were actually outscored in 2018, one reason Jerry Dipoto was willing to break up the roster. A key reason they still won 89 games was that Edwin Diaz crushed it as closer, with 57 saves. Strickland has to lock down the ninth or those one-run victories could turn into one-run losses. -- Schoenfield

Best case: Given the evolving nature of this mostly young team, the expectations won't be enormously high for Toronto in 2019. The Blue Jays' best-case scenario would certainly be a postseason berth, but with the mighty Yankees and Red Sox also in the division, that would be quite the accomplishment. Perhaps more realistically, an 85-win year and a (mostly full) season of fun feats from Vladimir Guerrero Jr. would make it a great year.

Worst case: Speaking of Guerrero, Toronto's plans relative to the 20-year-old's service time were well-documented ahead of the oblique strain that's currently sidelining him. Still, whenever the rookie does arrive in Toronto this year, the baseball world will deify him. Bo Bichette and Cavan Biggio, other sons of former big-leaguers, could make their big-league debuts this year, too. If the trio disappoints, struggling whenever they each reach The Show, Toronto's worst-case scenario would be realized.

Make-or-break player: Even if he misses the first few weeks, Guerrero will be the most-watched rookie across North America this season. Quite frankly, based on the way he raked in the minor leagues last year, there's little reason to believe Guerrero, if healthy, won't have immediate success in the big leagues. That arrival could be the jolt Toronto needs to fulfill its best-case scenario. -- Harvey

Best case: A wild card. Look, do the Padres appear as strong as the NL East or NL Central teams? No, but the projections see them around .500, which puts them in the hunt. They'll need the young rotation to mature overnight, Manny Machado to have an MVP-type season and the outfield corners (Wil Myers, Franmil Reyes, Hunter Renfroe) to combine for 60-plus home runs. Fernando Tatis Jr. could make a quick leap to stardom as well.

Worst case: The inexperienced rotation cracks, the middle infield youngsters aren't ready, the outfield corners can't stay healthy and Machado finds out that hitting home runs in Petco Park is a lot more difficult than it was at Camden Yards. The Padres match last year's 66-96 record.

Make-or-break player:Eric Hosmer. Obviously, a lot rides on the starting pitcher, but Hosmer needs to better justify the $144 million investment in him after a 1.4-WAR season that saw him hit .253/.322/.398. -- Schoenfield

Best case: The younger members of the young Pale Hose must take a collective step forward, with the hurlers in the bunch avoiding any more Tommy John surgeries. With Michael Kopech and Dane Dunning out, Chicago needs the likes of Lucas Giolito, Reynaldo Lopez, Dylan Cease and Carlos Rodon to show they are the makings of a productive big-league rotation. Just as badly, Chicago needs Yoan Moncada and Tim Anderson to show that they will be viable regulars as the next wave of position prospects reaches the South Side.

Worst case: Zero progress from the aforementioned prospects. The White Sox need to establish some momentum and brand themselves as a team on the verge of breaking through, because another tepid free-agent season could start to become a trend.

Make-or-break player: The void left by the failed pursuit of Manny Machado is the toughest to fill: the cornerstone piece. The face of the franchise. Or, analytically, the 5-8 wins around which you can build a roster on an annual basis. After committing to Eloy Jimenez, who has yet to log a single day of big-league service time, the White Sox badly need him to become what Machado already is. No, he likely can't establish that as a rookie, but he can show everybody that he's capable of scaling those heights. -- Doolittle

Best case: In their final season at Global Life Park before moving across the parking lot into a new venue, the Rangers need their young hitters to establish themselves -- finally -- as the foundation to Texas' next contending club. Rougned Odor must consolidate his gains from 2018. Nomar Mazara needs to approach stardom. Joey Gallo needs to be more consistent. Delino DeShields, Ronald Guzman and Willie Calhoun all need to progress. If most of these things happen, the Rangers' near-term future starts to come into focus.

Worst case: If most of those free-swinging hitters stagnate and Texas' M.A.S.H. unit of a starting rotation crumbles, things could get ugly. The Rangers have one of baseball's best relievers in Jose Leclerc, but the poor guy is only good for 70 innings or so.

Make-or-break player: In terms of Texas' 2019 outlook, it's not really one player but five: Mike Minor, Lance Lynn, Shelby Miller, Drew Smyly and Edinson Volquez. Can any of these guys even qualify for the ERA title? On the flip side, all are familiar names for a reason. Namely, they've all had success at the big-league level. If Jon Daniels hits the jackpot and the core rotation accounts for 130 or more starts, the Rangers can be competitive, even if a postseason push seems like the outer edge of possibility. -- Doolittle

Worst case: The reality is that the Giants' roster is littered with players who are past their primes and overly expensive. Their outfield lacks talent and their pitching staff lacks depth. The Giants need to begin their rebuild, and the 2019 season will probably validate that thinking.

Make-or-break player: Posey didn't hit for much power through the first five months of 2018, then underwent hip surgery in late August, raising questions about his long-term future behind the plate. Posey is still among the game's best catchers, but he is guaranteed more than $64 million over these next three seasons. The Giants need him healthy and right. -- Gonzalez

Best case: For the Detroit rebuild to start to look like something, the Tigers need some under-25 talents to reach the majors and flash their potential. Christin Stewart should see some big-league time, so if he does well and if Daz Cameron can push his way to the majors later in the season, that would be a start. If those guys progress and Miguel Cabrera comes back strong enough to give fans some career milestones to root for, that's a good season.

Worst case: The injury to Michael Fulmer may already be the first step toward a worst-case scenario in Detroit. Not only was he the Tigers' best pitcher -- and possibly their best player overall -- but he was also the last, best trading chip for Al Avila. Fulmer's Tommy John surgery could mean that his peak trade value has already come and gone. Tack that onto another season with what feels almost entirely like a stopgap roster, and it might be a dreary summer for the Tigers.

Make-or-break player: Fulmer's injuries probably intensify the need for the Tigers to get an exciting full-season debut from Casey Mize. The performance wouldn't be in Detroit, and it wouldn't have to be to satiate Tigers fans. They just need a whiff of ace-level buzz from somewhere in the organization. -- Doolittle

Best case: The Royals won 58 games last year. That's bad baseball. Sure, a quick turnaround is possible -- the Twins went from 59 wins to 85 and a wild card in 2017 -- but unlikely. The Royals will be kind of fun to watch with Whit Merrifield, Billy Hamilton and Adalberto Mondesi running wild on the bases, but there isn't much power here or on-base ability in the lineup. PECOTA forecasts 72 wins, FanGraphs 68, so a .500 season would be a huge step forward.

Worst case: Hamilton and Mondesi each steal 50 bases while posting .275 OBPs. Ryan O'Hearn hits like he did in Triple-A. Brad Keller can't repeat his low strikeout rate/low ERA rookie season. The bullpen is as bad it looks on paper. Another 58-104 season.

Make-or-break player: O'Hearn is fascinating. He was so good in his major league call-up -- .262/.353/.597, 12 home runs in 149 at-bats -- that there is some talent there. But he was awful in Triple-A (.232/.322/.391) and doesn't really have much of a track record in the minors. He could be the Royals' All-Star rep, or he could end up back in Omaha. -- Schoenfield

Best case: The Marlins are still early in their process, to the point that their best case would be the worst case for about half the other teams in the majors. What Marlins fans can hope for is that the makings of a dynamic young starting rotation start to come together around a lineup that at the very least plays the game the right way. Jordan Holloway, Trevor Rogers, Sandy Alcantara, Jordan Yamamoto, Edward Cabrera, Zac Gallen, Sixto Sanchez, Jorge Guzman, Nick Neidert, Braxton Garrett -- these are names in the system that Miami will monitor in the coming season. If most of those guys progress, the light at the end of the tunnel starts to grow a little brighter.

Worst case: More than anything, the Marlins can't afford the loss of forward momentum. They need their young big leaguers like Lewis Brinson, Jorge Alfaro and Brian Anderson to cement themselves as regulars. They need some of those young pitchers to break through. They need to keep their young arms healthy. Basically, Marlins fans have to be shown that all of this has been done for a reason, which won't be easy with Giancarlo Stanton, Marcell Ozuna, Christian Yelich and J.T. Realmuto all starring for contending teams.

Make-or-break player: Brinson was dreadful at the plate in his first Marlins campaign. It didn't help that the player he was traded for -- Yelich -- won the NL MVP award. Brinson doesn't have to do that. He just needs to look like a bona fide regular. -- Doolittle

Best case:Chris Davis parties like it's 2015 and puts up MVP numbers. Dylan Bundy remembers how to keep the ball in the park. Outfield prospect Yusniel Diaz, acquired in last summer's Manny Machado trade, explodes onto the scene in a Juan Soto kind of way and, along with fellow youngsters Cedric Mullins and Ryan Mountcastle, helps the Baby Birds take flight ahead of schedule. Instead of winning 63 games as projected, the O's shock the world by winning ... 73.

Worst case: Completely overmatched by their division rivals, the Orioles go a combined 0-38 against the Red Sox and Yankees. The rotation, long a sore spot in Baltimore, is so bad that new skipper Brandon Hyde opts for the opener strategy. Except that the bullpen -- minus longtime stalwarts Zack Britton, Brad Brach and Darren O'Day -- can't handle the added stress and completely implodes. Instead of winning 63 games as projected, the O's shock the world by winning ... 36.

Make-or-break player: Mike Elias. OK, so he's not actually a player. But more than anyone, Baltimore's new GM is the one who hold the keys to the team's success. How quickly Elias establishes the Birds' international pipeline, how well he drafts in June and how well he trades in July will be critical to the club's monster rebuild. -- Matz